// run: $exec < input
#include <iostream>
#include <algorithm>
#include <string>

int const maxn = 100007;
unsigned f[maxn][2];
int n;
std::string s;

int main()
{
	std::ios::sync_with_stdio(false);
	std::cin >> n >> s;
	if (n & 1) { std::cout << "0\n"; return 0; }
	int cq = 0;
	for (auto i : s) cq += (i == '?');
	int now = 0, prev = 0;
	f[0][now] = 1;
	for (int i = 0; i < n; i++) {
		prev = now; now ^= 1;
		if (s[i] == '?') {
			f[0][now] = f[1][prev];
			for (int j = 1; j <= std::min(i + 1, n - i); j++)
				f[j][now] = f[j - 1][prev] + f[j + 1][prev];
		} else {
			f[0][now] = 0;
			for (int j = 1; j <= std::min(i + 1, n - i); j++)
				f[j][now] = f[j - 1][prev];
		}
	}
	for (int i = 0; i < cq - n / 2; i++)
		f[0][now] *= 25;
	std::cout << f[0][now] << '\n';
}

